The Edelbrock #608115 Performer RPM cylinder heads are designed for 1958-1965 Chevrolet “W” Series 348/409 big-block applications. The Edelbrock #608115 Performer RPM heads are perfect for street performance, daily drivers, street rods and muscle cars where seat-of-the-pants performance is needed. These cylinder heads deliver great throttle response and power from 1500 to 6500 rpm. They also feature the highest quality intake and exhaust valves and valve springs. For use on pre-pollution controlled vehicles only.